Over the past several decades, the amount of electronics in automobiles, and other on-road and off-road vehicles such as pick-up trucks, commercial trucks, semi-trucks, motorcycles, all-terrain vehicles, and sports utility vehicles (collectively “motor vehicles”). Electronics are used to improve performance, control emissions, and provide creature comforts to the occupants and users of the motor vehicles. Motor vehicles are a challenging electrical environments due to vibration, heat, and longevity. Heat, vibration, and aging can all lead to connector failure. In fact, loose connectors, both in the assembly plant and in the field, are one of the largest failure modes for motor vehicles. Considering that just the aggregate annual accrual for warranty by all of the automotive manufacturers and their direct suppliers is estimated at between $50 billion and $150 billion, worldwide, a large failure mode in automotive is associated with a large dollar amount.
Considerable time, money, and energy has been expended to find connector solutions that meet all of the needs of the motor vehicles market. The current common practice is to use an eyelet and threaded fastener on all high-power connections. The current common practice is expensive, time-consuming, and still prone to failure.
A more appropriate, robust connector solution must be impervious to vibration and heat. In order to create a robust solution, many companies have designed variations of spring-loaded connectors, which have a feature that retains the connector in place. Such spring-actuated connectors typically have some indication to show that they are fully inserted. Sometimes, the spring-actuated feature on the connector is made from plastic. Other times, the spring-actuated feature on the connector is fabricated from spring steel. Unfortunately, although the current state of the art is an improvement over connectors using an eyelet and threaded connector, there are still far too many failures.
Part of the reason that spring-actuated connectors still fail in motor vehicle applications is because the spring element is on the periphery of the connector. By placing the spring tab on the exterior surface of the connector, connector manufacturers tried to make engagement obvious to the person assembling the part. Unfortunately, for both plastic and metal, the increased temperatures of an automotive environment make a peripheral spring prone to failure. The engine compartment of the motor vehicle can often reach temperatures approaching 100° C., with individual components of a motor vehicle engine reaching or exceeding 180° C. At 100° C., most plastics start to plasticize, reducing the retention force of the peripheral spring-actuated feature. At 100° C., the thermal expansion of the spring steel will reduce the retention force of a peripheral spring-actuated connector by a small amount. More important, with respect to spring-actuated features fabricated from spring steel is the effect of residual material memory inherent in the spring steel as the spring steel is thermally cycled. After many temperature cycles, the spring steel will begin to return to its original shape, reducing its retention force and making is susceptible to vibration. The motor vehicle market needs a connector that is low-cost, vibration-resistant, temperature-resistant, and robust.